EXPERIMENTAL INVESTIGATIONS OF WETTABILITY ALTERATION DUE TO VARIOUS NANOPARTICLES: AN EOR IMPLICATION WITH NANOFLUIDS

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1 SCA /6 EXPERIMENTAL INVESTIGATIONS OF WETTABILITY ALTERATION DUE TO VARIOUS NANOPARTICLES: AN EOR IMPLICATION WITH NANOFLUIDS Luky Hendrningrt nd Ole Torsæter Norwegin University of Science nd Technology (NTNU) This pper ws prepred for presenttion t the Interntionl Symposium of the Society of Core Anlysts held in Avignon, Frnce, 8-11 Septemer, 14 ABSTRACT This study investigtes the dynmic interctions of fluid-rock through wettility modifictions mong cores nd qurtz plte solid-phses with crude oil s n oleic-phse nd vrious hydrophilic nnoprticles dispersed in synthetic sewter s n queous-phse to revel its role during flooding s novel enhnced oil recovery method. Two solid sustrtes were employed (qurtz glss pltes nd Bere sndstone outcrops) with different initil wettility properties (wter-wet nd oil-wet). Severl prmeters were evluted, including wter slinity, ionic composition, different types nd concentrtion of nnoprticles, initil medium wettility, solid system, soking time nd stilizer presence. These prmeters drmticlly lter the sustrte wettility with time. The incorportion of hydrophilic nnoprticles cused the medi to ecome more wter-wet in ll wettility systems. In ddition, soking time with nnoprticles significntly ltered the wettility of the porous medium. These results demonstrte tht wettility cn e ltered s possile displcement mechnism when using nnoprticles in flooding processes. INTRODUCTION Understnding the reltionships mong wettility, cpillry pressure nd the distriution of oil nd wter in pore spces is criticl for optimizing oil recovery nd is necessry, difficult step in quntifying wettility nd its reltion to oil recovery (Morrow, 1990). These reltionships re complex within crude oil/rine/rock (COBR) systems ecuse of the complexity of pore structures nd reservoir rocks minerlogy (Morrow, 1990). The im of this study is to revel possile oil displcement mechnisms for enhnced oil recovery with NPs (Nno-EOR). This pper investigtes vrious types of hydrophilic nnoprticles (NPs) tht my ffect wettility when they re dispersed in synthetic sewter (SSW) s model formtion rine. The dynmic wettility modifiction due to the hydrophilic nnoprticles ws monitored y contct ngle mesurement under mient conditions. Severl prmeters were evluted during fluid-rock interctions, including slt concentrtion, wter slinity, different types of NPs, initil medium wettility, concentrtion, solid system, soking time nd stilizer presence. EXPERIMENTAL In this study, severl types nd sizes of hydrophilic NPs from Evonik Deguss were employed, including silic (SiO 2 ), lumin (Al 2 O 3 ) nd titni (TiO 2 ). Tle 1 summrizes the NPs properties.

2 SCA /6 Tle 1. Nnoprticles properties Properties SiO 2 Al 2O 3 TiO 2 Specific surfce re, BET (m 2 /g) 0± 65±10 ±15 Declred primry prticle size (nm) Bulk density (g/l) 1 ph (4-5% in dispersion) Their fluid properties re shown in Tle 2. The slinity is mesure of the totl dissolved slt ut is often used interchngely with totl dissolved solid (TDS), which is defined s the mount of ll inorgnic nd orgnic non-prticulte mteril (Houston, 07). Bsed on representtive se wter composition nlyses from sedimentry sins round the world (reported y Houston in 07), the mjor slt components re N +, K +, C 2+, Mg 2+, Cl -, HCO 3 - nd SO 4 2-, with ph rnging from 5.73 to 6. nd TDSs rnging from hundreds to 0,000 ppm. In this study, sodium chloride (NCl) t 3.0 wt.% (TDS pprox.,000 ppm) nd de-ionized wter were used s the se SSW. The other SSW with compositions/ slinities from 3,000 to 100,000 ppm were mixed with NPs. SSW type Tle 2. Synthetic sewter (SSW) properties Composition TDS, ppm Density, g/cm 3 Viscosity, cp ph Surfce Conductivity, mv A NCl 3.0 wt.%, B NCl 0.3 wt.% 3, C NCl 10 wt.% 100, D KCl 3.0 wt.%, E NCl (2.7%) + CCl 2.2H 2O (0.57 wt.%), F NCl (2.7%) + MgCl 2.6H 2O (1.01 wt.%), Vrious types of NPs were dispersed in vrious SSW t 0.05 wt.% for the se nnofluid concentrtion with SiO 2 NPs. This concentrtion ws selected sed on our previous concentrtion optimiztion study using silic NPs (Hendrningrt et l., 13). The nnofluid ws synthesized using high-speed mgnetic stirring nd gitted with ultr-soniction t - 100% mplitude (output power Wtt). A stilizer, polyvinylpyrrolidone (PVP), ws used t 1.0 wt.% to void erly ggregtion (Hendrningrt et l., 14). The nnofluid properties re presented in Tle 3. Bere core specimens nd rectngulr trnsprent pltes of qurtz were employed in this study s solid sustrtes. Severl core specimens nd qurtz pltes were initilly rinsed with methnol nd then distilled wter, nd dried in heting cinet t - C for severl dys. Ech mesurement used new solid sustrte. Hendrningrt et l. (13) reported tht the originl wettility of qurtz pltes nd Bere cores cn e oserved y mesuring the contct ngle in crude oil/rine/rock (COBR) systems, which re considered to e strong wter-wet (SWW). Energy-dispersive X-ry (EDX) nd X-ry diffrction (XRD) were performed for the minerlogicl identifiction of the Bere cores. Similr results hve een reported y Hendrningrt nd Torsæter (14) tht demonstrte tht the cores re composed primrily of qurtz (83-93 wt.%) with minor minerls, such s lkli feldspr (mx 8 wt.%) nd pyroxene (<1 wt.%). Therefore, it is ssumed tht our initil minerlogy dt re representtive of the entire core specimens studied in this work. For oil-wetting mesurement, chemicl mixture of % (V/V) pentne (C 5 -H 12 ) nd % (V/V) Surfsil TM (C 8 -H 24 -Cl 2 -O 3 -Si 4 ) ws prepred to lter the qurtz plte wettility from SWW to oil-wet (I W rnged from -0.5 to -0.6). This process took

3 SCA /6 pproximtely 6 dys t room conditions, which ws similr to the core ging from other studies. Tle 3. Nnofluid properties under mient conditions Nnofluid Composition Density, g/cm 3 Viscosity, cp ph Surfce Conductivity, mv A SSW-A + SiO wt.% B SSW-B + SiO wt.% C SSW-C + SiO wt.% D SSW-D + SiO wt.% E SSW-E + SiO wt.% F SSW-F + SiO wt.% G SSW-A + PVP 1 wt.% H SSW-A + Al 2O wt.% + PVP 1 wt.% I SSW-A + TiO wt.% + PVP 1 wt.% J SSW-A + SiO wt.% + PVP 1 wt.% K SSW-A + SiO wt.% L SSW-A + SiO wt.% + PVP 1 wt.% The contct ngle of the COBR system ws mesured directly on solid sustrtes (qurtz plte nd Bere core specimen) using Goniometry KSV CAM instrument under mient conditions for 3-6 hours, s shown in Figure 1. The system consists of qurtz plte/bere core specimen s the solid sustrte, crude oil s the oleic-phse nd nnofluid s the queous-phse. The contct ngle is mesured using formul s follow: where σ descries the interfcil tension components of phse, indices s, o nd w stnd for solid, oleic nd wter phses nd θ is the contct ngle. Treier et l. (1971) defined the contct ngle in 3-phse system (wter, oil nd rock) s follows: wter-wet in rnge from 0 to 75, intermedite/neutrl-wet from 75 to 105 nd oil-wet from 105 to 1. A contct ngle of 0 represents tht denser fluid is completely wetting the solid. Fig. 1 Contct ngle mesurements using the Goniometry KSV CAM instrument

4 Contct ngle of Aqueous phse, Contct ngle of Aqueous phse, SCA /6 RESULTS AND DISCUSSION The dynmic wettility modifiction, s ssessed y contct ngle mesurement under mient conditions, is shown from Figure 2 to Figure 5. Severl prmeters were evluted during the fluid-rock interction, such s the slt concentrtion, wter slinity, different types of NPs, initil medium wettility, concentrtion, solid system, soking time nd stilizer presence. There re severl essentil findings within this prticulr study. Effect of wter slinity (Wter-wet qurtz plte) Nnofluid-A Nnofluid-B Nnofluid-C 90 Effect of ionic compositions (Wter-wet qurtz plte) SSW-A SSW-D SSW-E SSW-F Nnofluid-A Nnofluid-D Nnofluid-E Nnofluid-F Figure 2 Wettility ltertion ws determined y contct ngle mesurements on wter-wet qurtz pltes. Effects of wter slinity nd ionic compositions We show on Fig. 2 tht incresing slinity (sodium chloride) of the wter with 0.05 wt.% NPs from 3,000 to 100,000 ppm is effective t ltering the wettility towrd more wterwet system. Bsed on the contct ngle mesurements on Fig. 2, oth monovlent nd divlent ctions cn increse the of wter-wetness of the system. The chnges in contct ngle with the presence of monovlent ctions (N + nd K + ) nd NPs exhiit similr potentil for modifying the rock wettility. Menwhile, divlent ctions ions, such s C 2+ nd Mg 2+, hve greter effects on the rock surfce nd lter the rock wettility. These oservtions re in ccordnce with Jr et l. (13) in cronte rocks. Active divlent ions, such s C 2+, Mg 2+ nd SO 2-4, more effectively decrese the chrged density. Consequently, more divlent ions cn contct the grin surfce nd lter the wettility (Austd, 13). These chnges might occur due to the dsorption of NPs, involving physicochemicl interctions during trnsport through the porous medium, resulting in wettility ltertion (Zhng et l., 13). The different types of NPs lso provided different responses to wettility modifiction in wter- nd oil-wet systems s shown in Fig. 3 nd 3, respectively. In wter-wet systems, once the hydrophilic metl oxide (with PVP) is introduced into the rine, the contct ngle is further reduced, which mens tht the metl oxide-sed nnofluids render the qurtz plte more wter-wet. The gretest reduction in contct ngle ws chieved with the TiO 2 -sed nnofluid. Menwhile, different initil wettility systems hd different impcts on the wettility. Unlike in wter-wet systems, silic-sed nnofluids were more effective thn luminum-sed nnofluids t ltering the system towrd weker oil-wet condition. Unfortuntely, due to the poor clrity of the TiO 2 -sed nnofluid in the oil-wet system, the mesurements could not e performed. However, Ehtesi et l. (14) oserved tht rock wettility chnges from oil- to wter-wet fter tretment with TiO 2 nnoprticles. Hence, the selection of NPs type should consider the initil wetting condition of the rock to chieve effective wettility ltertion.

5 Contct ngle of Aqueous phse, Contct ngle of Aqueous phse, SCA /6 Figure 3 Wettility ltertion ws determined y contct ngle mesurements on qurtz pltes. Effects of nnoprticles type in wter- nd oil-wet systems The use of different sustrtes (Fig. 4) nd soking times (Fig. 4) lso ffected the wettility effect of the NPs. However, s reported y Morrow (1990), dt from qurtz pltes re limited in vlue ecuse qurtz is single minerl. If ny other minerls re present, the fluid-rock interctions might e more complex. The trend showed tht longer soking time ltered the system to ecome more wter-wet. Thus, NPs hve the ility to modify the wettility of sustrtes s function of their interction/contct time Effect of sustrte mteril (Wter-wet Qurtz nd Bere Plte) Bere with SSW-A Bere with Nnofluid-A Qurtz plte with SSW-A Qurtz plte with Nnofluid-A Effect of Soking Wter-wet Bere Sndstone with Nnofluid-A Figure 4 Wettility ltertion ws determined y contct ngle mesurements on wter-wet qurtz pltes nd Bere sndstones. Effects of sustrte mteril nd soking durtion Bere no soking Bere soking 24 hours Bere soking 48 hours Stilizers were dded to void the erly ggregtion of the NPs nd provided etter stility over longer periods. PVP (1 wt.%) dispersed with the model formtion rine cused the qurtz plte to ecome more wekly wter-wet s shown in Fig. 5. Incresing the nnofluid concentrtion further decreses the queous contct ngle, mking the system more wter-wet (Fig. 5). Therefore, the NPs concentrtion lso ffects the of wettility modifiction of the COBR system.

6 Contct ngle of Aqueous phse, Contct ngle of Aqueous phse, SCA / Effect of stilizer (PVP) on wter-wet qurtz plte SSW-A Nnofluid-A Nnofluid-G Nnofluid-J Figure 5 Wettility ltertion ws determined y contct ngle mesurements on wter-wet qurtz pltes. Effects of sustrte mteril nd soking durtion Effect of NPs concentrtion on wter-wet qurtz plte Nnofluid-G Nnofluid-J Nnofluid-L CONCLUSION We reveled tht hydrophilic nnoprticles (NPs) cn modify the wettility of medi. These ltertions in wettility depend on the NPs type nd concentrtion, of wter slinity, ionic composition, initil porous medium wettility, solid system, nd durtion of NP interction in the fluid-rock system. Bsed on this prticulr study, the use of PVP s stilizer did not influence the wettility. Our results demonstrte tht NPs wettility ltertion is possile displcement mechnism for flooding processes. ACKNOWLEDGEMENTS The uthors grtefully cknowledge the Deprtment of Petroleum Engineering nd Applied Geophysics (NTNU) for the finncil support necessry to complete this study nd the permission to pulish this rticle. REFERENCES 1. Austd, T. 13. Smrt Wter s EOR Fluid in Crontes nd Sndstones: Chllengers nd Possiilities. Society of Petroleum Engineers. Extended strcts of SPE Workshop in Artic. Hrstd, Norwy. 2. Ehtesi, H., Ahdin, M.M., Tghikhni, V., nd Ghznfri, M.H. 14. Enhnced Hevy Oil Recovery in Sndstone Cores Using TiO Nnofluids. Energy Fuels 28 (1): Hendrningrt, L., Li, S., nd Torseter, O. 13. Enhncing Oil Recovery of Low-Permeility Bere Sndstone through Optimised Nnofluids Concentrtion. Society of Petroleum Engineers. Pper SPE MS. doi: / ms. 4. Hendrningrt, L. & Torseter, O. 14. Metl Oxide-sed Nnoprticles: Reveling Their Potentil to Enhnce Oil Recovery in Different Wettility Systems. Appl Nnosci:1-19. doi: /s Houston, S. J. 07. Formtion Wters in Petroleum Reservoirs: Their Controls nd Applictions. PhD thesis, University of Leeds. 6. Jr, M. Y., Al-Hshim, H. S., nd Adllh, W. 13. Effect of Brine Composition on Wettility Altertion of Cronte Rocks in the Presence of Polr Compounds. Society of Petroleum Engineers. SPE MS. doi: /1667-ms. 7. Morrow, N.R Wettility nd Its Effect on Oil Recovery. J. Pet Tech 42 (12): SPE PA. doi: /21621-pa. 8. Treier, L.E., Dune, L.E., Archer, L., nd Owens, W.W A Lortory Evlution of The Wettility of Fifty Oil-producing Reservoirs. SPE Journl (12): Zhng, T., Murphy, M., Yu, H., Bgri, H., Nielson, B., Bielwski, C., Johnston, K., Huh, C., nd Brynt, S. 13. Investigtion of Nnoprticle Adsorption during Trnsport in Porous Medi. Society of Petroleum Engineers. Pper SPE MS. doi: / ms.